Annular combustors

ABSTRACT

THE DISCLOSURE ILLUSTRATES AN ANNULAR COMBUSTOR HAVING AIR INLETS IN THE UPSTREAM END OF THE COMBUSTOR TO ESTABLISH A VORTES FLOW OF COMBUSTION GASES ADJACENT THE COMBUSTOR FUEL NOZZLES. A PAIR OF RELATIVELY LARGE LATERALLY SPACED DUCTS DOWNSTREAM OF EACH FUEL NOZZLE DIRECT A FLOW OF AIR TOWARD THE HEAD END OF THE COMBUSTOR TO REINFORCE THE VORTEX FLOW AND DEFLECT IT INTO A HORSESHOE SHAPE HAVING DOWNSTREAM EXTENDING LEGS. THE AIR FROM THE LATERALLY POSITIONED DUCTS PROMOTES CIRCUMFERENTIAL RECIRCULATION NEAR THE FUEL NOZZLES TO STABILIZE COMBUSTION. A PAIR OF RELATIVE SMALLER DOWNSTREAM DUCTS PROVIDE STREAMS OF VORTEX FLOW.

June 20, 1972 B. W. DOYLE 3,671,171

ANNULAR COMBUSTORS Filed NOV. 2'7, 1970 INVENTOR. BRIAN W. DOY LE BY W W 2W ATTORNEYS.

United States Patent 3,671,171 ANNULAR COMBUSTORS Brian W. Doyle, Shelton, Conn., assignor to Avco Corporation, Stratford, Conn.

Filed Nov. 27, 1970, Ser. No. 93,120 Int. Cl. F231 1/00, 9/00 US. Cl. 431116 Claims ABSTRACT OF THE DISCLOSURE The disclosure illustrates an annular combustor having air inlets in the upstream end of the combustor to establish a vortex flow of combustion gases adjacent the combustor fuel nozzles. A pair of relatively large laterally spaced ducts downstream of each fuel nozzle direct a flow of air toward the head end of the combustor to reinforce the vortex flow and deflect it into a horseshoe shape having downstream extending legs. The air from the laterally positioned ducts promotes circumferential recirculation near the fuel nozzles to stabilize combustion. A pair of relatively smaller downstream ducts provide streams of air that stabilize the downstream extending legs of the vortex flow.

The present invention relates to gas turbine engine combustors and more specifically to annular combustors.

Recent developments in the combustor designing art have achieved new forms of highly efiicient combustors. One such type may be found in the copending patent application entitled Annular Combustor, in the name of Jerry O. Melconian, Ser. No. 92,808, filed Nov. 25, 1970, and of common assignment with the present invention. This type of combustor incorporates ducts for inducing a circumferentially extending vortex flow adjacent the combustor fuel nozzles. A jet of air downstream of the nozzles reinforces the vortex flow and splits it into a pair of spaced downstream extending legs. This enables the combustion gases to be uniformly distributed in the combustor while at the same time reducing the number of nozzles required for this distribution by one half.

With such a design it has been found that there is a tendency for the jet to rapidly split the flow from the nozzle so that any imbalance in the spray pattern from the nozzle causes an inbalance in the temperature of the downstream legs of vortex flow.

Accordingly, it is an object of the present invention to provide a jet pattern in a combustor of the above type which provides substantially uniform flow and temperature in the combustor irrespective of the distribution from a fuel nozzle.

These ends are achieved by means that define a pair of laterally spaced relatively large openings for reinforcing and deflecting the vortex flow in a combustor of the above type so that a substantial circumferential recirculation is established in the vortex flow adjacent the nozzle to equalize the distribution of combustion gases in the dowstream vortex legs.

The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawing and the novelty thereof pointed out in the appended claims.

In the drawing:

FIG. 1 is a fragmentary longitudinal sectional view of a gas turbine engine which incorporates an annular combustor having a jet design which embodies the present invention;

FIG. 2 is a view taken on lines 2-2 of FIG. 1 showing the annular combustor of FIG. 1 in an unwrapped condition;

FIG. 3 is a view taken on lines 33 of FIG. 1.

3 ,6 71,17 1 Patented June 20, 1972 "ice Referring particularly to FIG. 1, there is shown an outer housing 10 for a gas turbine engine, only a portion of which is shown, and a diffuser duct 12 cooperating with the outer housing 10 to provide an annular peripheral flow path for pressurized air from a compressor (not shown). The air that passes from the diffuser duct 12 enters a chamber 14 formed by the housing 10 and a coaxial turbine outlet duct 16.

Positioned in the pressure chamber 14 is an annular combustor generaHy referred to by reference character 18. Combustor 18 comprises inner and outer walls 20, 22, respectively, which are secured to an upstream closed end 24 having a series of circumferentially spaced fuel nozzles 36 (only one is shown). The inner and outer walls 20, 22 join outer and inner turbine inlet ducts 26, 28 by a sliding thermal expansion joint to form an open downstream outlet 30.

A turbine inlet nozzle assembly 32 is secured to the downstream end of turbine inlet ducts 26 and 28. A bladed rotatable turbine wheel 34 is positioned downstream of nozzle 32. Turbine wheel 34 may be one of a series of turbine wheels positioned along dashed line 35 that are rotated by passage of hot gases from the turbine nozzle 32. However, only turbine wheel 34 is shown to simplify the description of the invention.

In operation of the engine, pressurized air in chamber 14 enters the interior of combustor 18 through openings to be described in detail later and fuel is injected into the combustor 18 by fuel nozzles 36. The fuel is mixed with air and the mixture ignited by suitable means to provide a hot propulsive gas stream. The hot gas stream flows to the downstream outlet 30 and is discharged from turbine inlet nozzle assembly 32 across bladed turbine wheel 34. The rotating output of turbine wheel 34 is generally used to drive a bladed compressor which supplies pressurized air for the combustor 18. Downstream of turbine wheel 34 the hot gases may pass through successive power turbine stages driving an output shaft or may be discharged through a nozzle to provide a reaction propulsion for the engine.

The upstream closed end 24 of the combustor 18 joins the outer wall 22 at a series of corrugations 38. The net effect of this is to form a plurality of inlet ducts 40 (see particularly FIG. 3) that admit pressurized air and direct it in an upstream direction, as shown by the arrows in FIG. 1, representing the flow of the air into the combustor. The upstream closed end 24 joins the inner wall 20 along a series of corrugations 42. This junction forms a series of inlet ducts 44 (see FIG. 3) which direct air into combustor 18 in a downstream direction, as shown in FIG. 1.

Directly downstream of the nozzles 36 are a pair of relatively large, laterally spaced flow deflecting inlet ducts 46. Preferably, these ducts are formed to direct flow into the combustor at an angle of 30 degrees relative to the normal plane of combustor 18, as shown in FIG. 1.

As is particularly apparent from FIGS. 1 and 2, the flow deflecting ducts 46 reinforce and establish a strong vortex flow immediately adjacent nozzles 36. The vortex flow has an axis of rotation extending circumferentially relative to the annular combustor 18. Since the ducts 46 are relatively large and spaced from one another, the vortex flow adjacent the nozzles 36 extends circumferentially for a substantial distance.

Once the vortex flow has gone beyond the end of ducts 46 it turns toward the outlet 30' in the form of two downstream legs L and L These legs extend toward the outlet 30 and their axis of rotation is generally parallel to the axis of the annular combustor.

To stabilize the vortex flow in these legs, a pair of relatively smaller ducts 48 are positioned downstream of the large ducts 46. The air from these jets stabilizes the vortex flow in the legs and maintains it in a uniform position. To cancel the vortex flow in legs L and L a series of cancelling jets are provided through openings 50, 52. These jets are positioned to oppose the direction of rotation of the vortex flow, as shown particularly in FIGS. 2 and 3. Once the vortex lflow in legs L and L has been cancelled, suitable diluting air is provided through openings 54 to cool the mixture for discharge from outlet 30.

Although it is not described herein, to enable a clearer understanding of the present invention suitable air inlets can be provided to film cool the inner and outer walls 20, 22, as is apparent to those skilled in the art.

During operation of the engine the air flow above causes a strong vortex flow immediately adjacent the nozzles 36 and for a substantial circumferential extent on either side of them. This vortex flow recirculates and maintains the hot downstream gases adjacent the nozzle to stabilize and maintain combustion. In addition, the spacing of ducts 46 causes a suitable circumferential recirculation of the gases which tends to even out any inbalance in the spray pattern of fuel from nozzles 36. This circumferential recirculation then causes the flow that is deflected into the downstream legs to be substantially uniform and have an even temperature distribution.

The small stabilizing jets downstream of the jets form ducts 4 6 to stabilize the legs of vortex flow and maintain them in relatively uniform positions. When the ducts 46 are formed to direct the flow in a forward direction, as shown in FIG. 1, they enable a substantial reduction in the air that is required to pass through the ducts to establish a strong vortex flow adjacent the nozzles 36. As an example, the illustrated angle of 30 degrees enables a reduction of between 10 and percent in the air required to establish a strong vortex flow. This enables a greater utilization of the available air for other purposes in the combustor.

It should be apparent to those skilled in the art that the parameters of the pressure in chamber 14, the desired energy release of the combustor 18, its physical dimensions, and the various air flow requirements, are utilized to provide jets from ducts 46 that have suflicient force to establish the vortex flow described above.

The construction above enables the same reduction in fuel nozzles for a given annular combustor as is described in the above reference to copending application in the name of Jerry O. Melconian. With this arrangement the combustion gases from each nozzle 36 are split and discharged over a wide circumferential distance in the combustor 18. The net effect of this distribution is to provide the equivalent of a combustor which utilizes twice the number of nozzles as annular combustor shown above. This is particularly illustrated in FIG. 2 where a series of center lines, designated N, are placed in line with the axes of the legs of vortex flow. If a conventional combustor utilizing swirl type flow around each nozzle were to be used, the axis of the fuel nozzles would fall along center lines N. It is apparent that this construction, while retaining excellent distribution, enables a substantial reduction in the cost of an annular combustor thereby permitting it to be used in relatively economical engines.

While the combustor design shown above has been described in connection with an engine of the reverse flow type, it is apparent that the combustor can be used in engines of the straight flow type by using suitable turning ducts without departing from the spirit and scope of the present invention.

Having described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. In a combustor comprising an annular walled chamber immersed in pressurized air and having an upstream closed end and a plurality of circumferentially spaced nozzles injecting fuel in an axial direction from the upstream end for combustion with pressurized air in said chamber and a downstream lower pressure open end for discharging combustion gases therefrom, the improvement comprising:

means formed in the walls of said annular chamber for directing pressurized air in a vortex flow closely adjacent said nozzles and having the axis of rotation of the vortex flow extending circumferentially relative to said annular chamber; and

means defining a pair of laterally spaced relatively large openings downstream of said vortex flow means for reinforcing and deflecting said vortex flow into two spaced downstream extending legs of vortex flow on either side of each of said nozzles, whereby a substantial circumferential recirculation is established in the vortex flow adjacent the nozzle to equalize distribution of gases in said downstream legs.

2. Apparatus as in claim 1 further comprising means for defining a pair of relatively smaller openings downstream of said relatively large openings for stabilizing the downstream legs of said vortex flow.

3. Apparatus as in claim 1 wherein the means for defining said relatively large jets comprises deflectors for directing the flow therefrom toward an upstream direction whereby the quantity of flow to reinforce said vortex and deflect it into said downstream legs is minimized.

4. Apparatus as in claim 3 wherein said deflecting means directs the flow from said relatively large jets at an angle of 30 degrees relative to the normal axis of said annular combustor.

5. Apparatus as in claim 4 further comprising means for defining a pair of relatively smaller jets downstream of said relatively large jets for stabilizing the downstream legs of said vortex flow.

References Cited UNITED STATES PATENTS 5/ 1970 Pierce 60-3965 X 7/1971 Gerrard 4l3352 EDWARD G. FAVORS, Primary Examiner 

